Bandgap reference circuits are used to provide a stable reference voltage independent of temperature variation. One continuous time bandgap reference circuit known as a Brokaw cell utilizes two matched bipolar transistors operating at different current densities to develop V.sub.BE which decreases with temperature and .DELTA.V.sub.BE which increases with temperature and scales the .DELTA.V.sub.BE with a resistor network to just offset the V.sub.BE decrease to produce the stabilized reference voltage. Another continuous time bandgap reference circuit fabricated in CMOS technology makes use of the parasitic substrate bipolar transistors to combine V.sub.BE and the offseting .DELTA.V.sub.BE to obtain the temperature stabilized reference output voltage. In the construction the transistors must be matched and the output is a high impedance instead of the operational amplifier of the Brokaw cell. In this construction and in the Brokaw cell the continuous nature of the output makes it difficult to correct the inherent amplifier offset.
In another approach, as disclosed in U.S. Pat. No. 5,563,504, Gilbert et al., a single PN junction is used to develop both the V.sub.BE and offsetting .DELTA.V.sub.BE but it is a switching band gap reference circuit which alternates between two modes: the auto-zero mode in which the output voltage is not temperature stabilized and the valid reference mode in which it is. The PN junction is typically a parasitic substrate bipolar transistor in a CMOS circuit. In these circuits the .DELTA.V.sub.BE is relatively quite small which does not help with signal to noise ratio considerations. One way to increase .DELTA.V.sub.BE is to increase the current density ratio but this only aids up to a point due to the logarithmic nature of .DELTA.V.sub.BE with respect to current density. Further, when the current density is increased the ability to match the PN junction becomes more difficult.